You can also give some high-calcium foods (like parsley) during lap time. For some reason, this makes it much more appealing, at least for my pigs. It also means the older pig won't get it. If you just leave it in the cage, he'll probably end up eating some and getting more calcium than he should, and the smaller one will get less.

Thank you everyone for your input! He's quickly learned to enjoy parsley which we give him at each meal - he's also learning to eat as fast as possible because the big pig tries to steal it!! We give him his bell pepper to keep him distracted!